1. Field of the Invention
The present invention relates to an optical lens assembly for image capture, and more particularly to an optical lens assembly for image capture comprised of three lens elements and applies to compact electronic products.
2. Description of the Related Art
In electronic products such as digital still cameras, mobile phone cameras and web cameras, an optical lens assembly for image capture is installed for capturing images, and the optical lens assembly tends to be developed with a compact design and a low cost, while meeting the user requirements for high resolution, good aberration correction, high image quality.
In general, a conventional optical lens assembly of a mini electronic product comes with different designs, including the two-lens, three-lens, four-lens, and five-or-more lens designs. If the image quality is taken into consideration, the optical lens assembly for image capture with the four-lens and five-lens designs have advantages on aberration correction and modulation transfer function (MTF) performance, yet they incur a higher cost, and the optical lens assembly for image capture with the two-lens design can hardly meet the high resolution requirement, and thus the optical lens assemblies for image capture with the three-lens design as disclosed in U.S. Pat. Nos. 7,706,086 and 7,460,314 and WIPO Pat. No. WO2010026689 are preferred.
In the optical lens assembly for image capture with the three-lens design, a combination of positive refractive power, negative refractive power and positive refractive power is generally adopted for the design, particularly the first lens element in proximity to the image plane is designed with positive refractive power to increase the width, and the conventional optical lens assembly is generally designed with a bi-convex lens or a convex meniscus lens in the object-side direction as disclosed in U.S. Pat. Nos. 7,710,662, 7,532,416, 7,529,041 and 2009/046380. Although these designs can provide more powerful positive refractive power to the first lens element nearest to the object side, the aberration and distortion of images caused by the second lens element and the third lens element cannot be compensated or corrected easily to meet the requirements for a high-quality optical lens assembly for image capture. To overcome the aforementioned drawback, the optical lens assembly for image capture as disclosed in U.S. Pat. No. 7,301,712 adopts the design of the first lens element having a concave object-side surface and the second lens element having a concave object-side surface, such that the positive refractive power of the first lens element will not be too large. Although the total length of this optical lens assembly for image capture can be shortened, the change of curvature of the second lens element is too large, such that the manufacture is not easy, and the refractive power of the second lens element is higher than the refractive power of the first lens element. As a result, the optical lens assembly for image capture has chromatic aberrations at the edges and more serious aberrations of the images. To overcome the drawbacks of the prior art, it is necessary to have a better design for compensating the aberration, limiting the total length of the optical lens assembly for image capture, and applying to mini electronic devices. Therefore, the present invention provides a feasible design and adopts a combination of refractive powers of the three lens elements and a combination of convex and concave lens elements to achieve the effects of providing a high image quality, facilitating mass production to lower the cost, and applying the optical lens assembly to electronic products.